404 DESCEIPTION OF PLATES. PLATE XXV. Urtica Beeweei, Watson.—Natural size. Fig. 1. Staminate flower. Fig. 2. PistiUate flower,Fig. 3. Achenium, enclosed by the large inner sepals. Fig. 4. Calyx, opened, showing mature ache¬nium. All enlarged about 10 diameters. PLATE XXVI. SiSYRINCHIUM Arizonicum, Eothr.—^Natural size. Fig. 1. Stamen, seen from outside. Fig. 2.Stamen, seen from inside. Fig. 3. Styles and stigmas. Fig. 4. Flower, divested of perianth. Fig. 5.Capsule. All enlarged. PLATE XXVn. Trisetum Wolfu, Vasey.—Fig. 1. Plant, natural size. Fig. 2. Spikelet, enlarged 5 times. Fig.3. Floret, showing the palets and hnear seed. Trisetum alpestre, Beauv.—Fig. 4. Natural size. Fig. 5. Spikelet, magnified 6 diameters.Fig. 6. Spikelet, with glumes removed. The last should have sho"wn a little pubescence on the stem.ofthe upper floret. Vilfa minima, Vasey.—^Fig. 7. Natural size. Fig. 8. Flower, enlarged 15 times. Fig. 9. Sectionof stem, greatly enlarged. PLATE XXVin. Poa Wheeleri, Vasey.—Fig. 1. Plant, natural size. Fig. 2. Spikelet, magnified 5 times. Fig.3. Upper floret, "with rudiment, enlarged 9 times. PLATE XXIX. Festuca Thurberi, Vasey.—Natural size. Fig. 1. Spikelet, enlarged 5 times. Fig. 2. Upperglume. Fig. 3. Lower glume. Fig. 4. Upper palet. Fig. 5. Lower palet. PLATE XXX. Notholmna Hookeri.—Ordinarj^ size. Fig. 1. Scale of the rootstock. Fig. 2. Scale from thobase of the stalk. Fig. 3. Segment of one of the pinnse, sho"wing the sporangia and the sUghtly recurvedmargin. The details are enlarged about 6 diameters.